Email Warmup Tools and Strategies for Cold Outreach

Email warmup is possibly the real unsung hero of cold email outreach. It is very easy for sales and marketing teams to become so engaged in generating the most perfect email content possible, creating the perfect segment, and even running A/B tests like there’s no tomorrow.

But all of these efforts will be for naught without a strong warmup—those “perfect” emails will still land in spam. And if those emails go unseen, then they’re not going to deliver the results you seek.

In this blog, we’re going to walk you through how to create an advanced email warmup strategy, designed specifically for cold outreach campaigns. We’ll also offer best practices for gradually increasing your email volume and explore some of the top email warmup tools that can automate this process, saving you time and effort while maximizing deliverability. 

What is email warmup and why is it important for cold outreach?

Email warmup is the process of slowly ramping up send volume from a new or inactive domain to establish a positive reputation with Email Service Providers (ESPs).

For cold outreach to work, your emails must be sent to inboxes where they stand the best chance of getting read and interacted with. If your emails are going to the spam folder, they aren’t going to be read, and you aren’t going to be getting any responses no matter how beautifully they’re written.

A good warm-up plan enables you to slowly introduce your emails to ESPs so that your domain gains trust from them slowly. This will give your cold outreach emails a better chance of avoiding spam filters.

Pursuing cold outreach efforts without proper warmup can damage your sender reputation. ESPs gauge how legitimate or spammy you may be largely based on your sender reputation. So if you send massive amounts of emails at an accelerated rate from an unfamiliar domain, you can expect that ESPs will tag your emails as spam—resulting in poor deliverability rates.

By not including any warmup, you risk:

• Being added to blacklists, which can drastically reduce the chances of your emails being delivered. (Read more: Are Blacklists Killing Your Emails? A Deep Dive into How They Influence Email Providers)
• Lower engagement rates due to emails being routed to spam or the promotions tab.
• A damaged sender reputation, making it harder to warm up other email accounts or future campaigns.

Best practices for effective email warmup

When a new email account is about to undergo warmup, it’s very important to follow some certain best practices if you’re looking to both establish a strong sender reputation and enjoy high deliverability. Here are best practices to maximize the effectiveness of your email warm-up strategy:

Gradually increase your email volume

The secret to an effective email warm-up is to start small and start slow. Email Service Providers (ESPs) might be suspicious about high volume emails coming from a new or inactive domain. If you send too many emails too soon, your domain will appear suspicious—ruining your sender reputation and sending your emails to the spam folder.

Gradual increases means you won’t be flooding the system, and ESPs will have a chance to identify your account as trustworthy. For example: 

• Week 1: Send around 10-20 emails per day. Keep the volume low or you might raise red flags.
• Week 2: Increase to 40-60 emails per day. Work on delivering personalized and relevant content to your audience.
• Week 3: You can begin sending up to 100 emails per day. Remember to ramp up this number gradually while maintaining consistent patterns. 
• Week 4 and beyond: Gradually increase your sending volume by 20-25% each week until you reach your target send volume.

While you increase your volume, do monitor your open rates and engagement rates regularly. Take note of sudden drops. If your open rates decreasing or your bounce rates are climbing, dial down the volume a bit.

🔖 Relevant Reading: How Long Does It Take to Warm Up an Email Domain for SaaS Companies?

Personalize your warmup sequences

Personalizing your warmup emails is crucial for simulating natural email behavior—plus, these types of emails deliver 6x higher transaction rates.

Generic emails come across as obviously automated and raise suspicion with ESPs. You wouldn’t go to a party and introduce yourself with the same 60 seconds of content over and over to everyone, would you? Instead, tailor your warm-up emails so they don’t look they’re being sent by a bot. They will be treated more likely as legitimate.

For instance, your warm-up sequence can include the person’s name, company name, or specific subject lines, etc. This gives your emails authenticity, and it makes your emails genuine—helping you build the trust with ESP’s.

Some examples:

• “Hi [Name], Let’s Get [Company] Connected”“
• Hi [Name], I figured it would be worth reaching out because I think [Company] could benefit from…”

Be consistent with your outreach

Staying consistent is the best way to build a solid email warm-up. ESPs search for trends in your email behavior and  abnormal email delivery (like sudden spikes or a long disappearance) raises concern.

During the warm-up phase, make sure your frequency level and content remains unchanged. Keep sending at a regular frequency and aim to ramp it up—but gradually. This consistency helps build trust with ESPs and increases the likelihood of successful email delivery. To simulate the patterns of actual sending, these are your best practices:

• Switch up the times and days you send emails. Randomize the sending schedule to simulate natural activity.
• Send emails at different times of day to show ESPs that your domain is engaging in organic, real human activity.
• Don’t send the same email over and over again. Try varying headlines, content, and even incorporate some personalization efforts. 

Focus on building a strong sender reputation

Sender reputation is one of the primary factors that determines email deliverability. Even the best emails can be sent to the spam folder without a positive reputation. However, building a solid sender reputation cannot happen overnight—it’s a long-term effort.

Senders must continue training Email Service Providers (ESPs) to trust them. One mistake and your reputation could be ruined, and you’d have a more difficult time reaching an audience in the future. Here are some tips to build a strong sender reputation:

• Maintain a clean email list: Get used to cleaning out invalid or old email addresses. A clean list means your emails are being delivered to active and engaged subscribers, which lowers bounce rates and increases deliverability. (Read more: 6 Must-Have Email List Scrubbing Tools for Spotless List Hygiene in 2025)
• Segment your audience: Don’t send the same message to everyone—segment your lists based on various criteria: demographics, behavior, and even patterns. Targeted and personalized emails are much more likely to be opened and engaged with, which helps your reputation.

For new domains or inactive domains, it will take more time to build a good reputation, and that’s where proper email warmup comes in. The Science and Process of Warming Up Newly Created Email Domains is a recent report from the Warmy Research Team. It details a comprehensive series of tests involving different email platforms and diverse domain configurations. 

5 email warmup tools for cold outreach

Email warmup tools help ensure your cold outreach emails land in the inbox instead of the spam folder. Since these warmup tools automate the process, they can safely ramp up your delivery volume and gain the trust of Email Service Providers (ESPs). Here are some of the best email warming tools that can help you reach people’s inboxes faster.

Lemwarm (Lemlist) for warmup automation and personalization

Lemwarm, part of Lemlist’s powerful cold email platform, focuses on automating your email warmup process while ensuring each email is personalized. It generates a tailored warm-up strategy based on sender’s answers to a few questions upon set up. 

Key features:

• Leverages more than 10,000 real users with domain ages reaching up to 25 years
• Easy-to-navigate user interface
• Dashboard contains insights on inbox placement, spam percentages, and suggestions for deliverability improvements

MailReach for simple, scalable warmup

MailReach is ideal for beginners who prefer simplicity over advanced customization. With its straightforward interface, MailReach helps ramp up sending volume in a controlled way, ensuring your email address gains trust with ESPs over time. 

Key features:

• Minimal configuration needed
• Provides a free email spam test to so your emails will not be flagged as spam.
• User-friendly dashboard with real-time email metrics tracking.

Instantly for fast and efficient warmup

Instantly is designed for users who need to warm up their email accounts quickly without sacrificing deliverability. With its fast set-up process, Instantly is most ideal for businesses looking to get up and running quickly.

Key features:

• One click activation for connecting your mailbox
• Provides a deliverability score and statistics on inbox placement
• Leverages their own network of over 1,000,000 real email accounts for warmup

Mailwarm for consistent warmup with no hassle

Mailwarm automates the email warmup process by creating daily interactions with other Mailwarm accounts. This behavior ensures that your emails are recognized as legitimate by ESPs. It requires minimal input, making it a great option for those seeking a set-it-and-forget-it solution.

Key features:

• Blacklist monitoring which alerts senders of any detected presence
• Can send up to 50 warmup emails per day on the basic plan, and up to 500 warmup emails sent daily on higher plan
• Easy setup with minimal user input
• Ability to pause or adjust intensity when needed

Warmy for all-in-one warmup and deliverability solution

Warmy.io stands out as the most comprehensive and powerful email deliverability tool on the market today. Brought forth to help businesses get the most out of their cold email efforts, Warmy guarantees your emails won’t just land in the inbox—but that they’re also optimized for numerous Email Service Providers (ESPs). 

Why Warmy is the best email deliverability tool for cold emailing